n = int(input())
ccc = input()
cnt_r = ccc.count('R')
ans = 0
for i in range(cnt_r):
    if ccc[i] == 'W':
        ans += 1
print(ans) n = int(input()) n int(input()) int input() input ccc = input() ccc input() input cnt_r = ccc.count('R') cnt_r ccc.count('R') ccc.count ccc count 'R' ans = 0 ans 0 for i in range(cnt_r):
    if ccc[i] == 'W':
        ans += 1 i range(cnt_r) range cnt_r if ccc[i] == 'W':
        ans += 1 ccc[i] == 'W' ccc[i] ccc i 'W' ans += 1 ans 1 print(ans) print ans cnt_r = ccc.count('R') ccc.count('R') cnt_r ans = 0 0 ans ans += 1 1 ans n = int(input()) int(input()) n ccc = input() input() ccc
n = int(input())
ccc = input()
cnt_r = ccc.count('R')
ans = 0
for i in range(cnt_r):
    if ccc[i] == 'W':
        ans += 1
print(ans)